Consider the following alternative. The forward-facing brain can almost certainly be traced back to the development of neural nets in all extremely simple organisms with bilaterian (symmetrical) body plans.

These theories remain controversial, but what is more established is that modern men's sexual organ size is disproportionately linked to how good they feel about their whole bodies, including how much they like their own face, and assess overall physical attractiveness. Researchers find almost 50% would prefer to have a bigger penis. Is this some kind of evolutionary competitive hangover?